N-Glycoproteomic Analysis of Chicken Egg Yolk

N-glycoproteomic profiling reveals structural and functional alterations in yellow primary preserved egg white under saline-alkali treatment

The posttranslational N-glycosylation of food proteins is important to their structure and function. However, the N-glycoproteomics of yellow preserved egg white were rarely reported. This study explored the changes of N-glycoproteome in yellow preserved eggs white after salt and alkali treatment. A total of 213 N-glycosites were identified on 102 glycoproteins, revealing prevalent glycosylation motifs and multiple N-glycosites within proteins. Salt and alkali treatment significantly altered the glycosylation patterns, impacting major proteins differently. GO analysis indicated the roles of differentially expressed glycoproteins in responding to stimuli and biological regulation. KEGG analysis emphasized the importance of salivary secretion pathway in enzyme secretion and peptide generation. Protein domain analysis highlighted the downregulation of Serpin. Protein-protein interaction networks revealed Apolipoprotein B as central players. This study provides essential structural information on the glycosylation modifications of egg white proteins, contributing to our understanding of the mechanisms behind the functional properties of preserved eggs.

Quantitative N-glycoproteomic analysis of egg yolk powder during thermal processing

The production of egg yolk powder often involves critical processes such as pasteurization and spray drying, however, these thermal processes will inevitably affect the functional properties of egg yolk (especially gelation and emulsification). The aim of this study was to elucidate the mechanism of the effect of pasteurized egg yolk (P-EY) and spray-dried egg yolk (SD-EY) on the functional properties through quantitative N-glycoproteomic. The results showed, compared with fresh egg yolk (F-EY), emulsifying property of mild heat-treated P-EY was slightly reduced while the gelation property did not undergo significant changes, whereas emulsifying activity (EAI) and gelation strength of vigorously heat-treated SD-EY were significantly reduced by 48.72 % and 35.73 %, respectively. During thermal processing in SD-EY, larger aggregate particles (particle size ∼10 um) were formed, and the surface hydrophobicity was reduced (93.0 %) and the zeta potential was enhanced (62.8 %). The results of quantitative N-glycoproteomic showed that 13 N-glycosylated proteins (APOB, vitellogenin, etc.) were down-regulated while only 2 N-glycosylated proteins were up-regulated; 21 N-glycosylation sites were down-regulated and 2 N-glycosylation sites were up-regulated in SD-EY, suggesting that covalent cross-linking of protein N-glycoproteins may have occurred in the process of spray-drying, which altered molecular physicochemical characteristics of the yolk solution that further affecting the processing properties of egg yolk.

Quantitative proteomic analysis of chicken egg white and its components

The protein profiles and properties of chicken egg white and its three components (thick egg white, TKEW; thin egg white, TNEW; and chalaza, CLZ) were comprehensively compared. The proteomes of TNEW and TKEW are relatively similar, but the abundance of mucin-5B and mucin-6 (the two subunits of ovomucin) is significantly higher in TKEW than in TNEW (42.97% and 870.04%, respectively), while the lysozymes in TKEW are 32.57% higher (p < 0.05) than those in TNEW. Meanwhile, the properties (including the spectroscopy, viscosity, and turbidity) of TKEW and TNEW are significantly different. Comprehensively, it is speculated that the electrostatic interactions between lysozyme and ovomucin are the main reason for the high viscosity and turbidity of TKEW. Compared with egg white sample (EW), CLZ has a higher abundance of insoluble proteins (mucin-5B, 4.23-fold; mucin-6, 6.89-fold) and a lower abundance of soluble proteins (ovalbumin-related protein X, 89.35% lower than EW; ovalbumin-related protein Y, 78.51% lower; ovoinhibitor, 62.08% lower; riboflavin-binding protein, 93.67% lower). These compositional differences should explain the insolubility of CLZ. These findings are important references for deepening the research and development of egg white in the future, such as the thinning of egg white, the molecular basis of changes in egg white properties, and the differential application of TKEW and TNEW.

Quantitative N-Glycoproteomic Analysis of Cattle-Yak and Yak Longissimus Thoracis

In this study, the N-glycosylated protein profiles of cattle-yak longissimus thoracis (CYLT) and yak longissimus thoracis (YLT) were comparatively analyzed using quantitative proteomics techniques. A total of 76 differential N-glycosylated proteins (DGPs) were screened from 181 quantified N-glycoproteins, indicating that differences in N-glycosylation levels are key to the differences between CYLT and YLT. In particular, a variety of N-glycoproteins involved in the extracellular matrix were differentially N-glycosylated between CYLT and YLT, mainly including fibrillin-1, fibromodulin, collagen, and laminins. In addition, the N-glycosylation levels of several lysosomal-related proteolytic enzymes (cathepsin D, dipeptidyl peptidase 1, legumain, and aminopeptidases, etc.) were significantly higher in CYLT. These results indicated that the N-glycosylation of CYLT and YLT proteins plays a crucial role in the regulation of extracellular matrix organization (muscle fiber structure) and lysosomal activity (postmortem meat tenderness). The results remind us that posttranslation modifications, especially N-glycosylation, are still icebergs beneath the surface.

Comparative N-Glycoproteomic Investigation of Eggshell Cuticle and Mineralized Layer Proteins

The eggshell cuticle layer (ECL) and eggshell mineralized layer (EML) contain amounts of glycoproteins and proteoglycans. However, there were few comprehensive reports about the effect of post-translational modifications on protein structure and function which requires investigation. Therefore, we used comparative N-glycoproteomics to study glycoproteins in the ECL and EML. We identified a total of 272 glycoproteins in this experiment and found that glycoproteins located in EML were more than that in ECL. Moreover, they showed distinct functional difference between both layers. As N-glycosylation of ovocleidin-17 and ovocleidin-116 in the EML affected eggshell mineralization, some glycoproteins located in ECL, like ovotransferrin and ovostatin-like, possessed antibacterial activity. The several regulated glycoproteins in the EML may pertain to the regulation of mineralization, while glycosylated proteins in the ECL may contribute to molecular adhesion and defense against microbial invasion. This study provides new insights into the eggshell matrix protein contents of the ECL and EML.

Research Note: Integrated proteomic analyses of chicken egg yolk granule

Chicken egg yolk granules (EYG) were the precipitated component of egg yolk after water dilution and centrifugation. Compared with egg yolk, EYG are rich in proteins, phospholipids, and minerals. In this study, an integrated proteomic analysis was carried out to in-depth mapping of the proteome, phosphoproteome, and N-glycoproteome of EYGs. After hydrolysis of the EYG total protein, the hydrolyzed peptides or the enriched phosphopeptides/glycopeptides were identified by liquid chromatography-tandem mass spectrometry. A total of 125 phosphorylation sites from 36 phosphoproteins and 244 N-glycosylation sites from 100 N-glycoproteins were identified in EYG. All 3 vitellogenins (precursors of egg yolk high-density lipoprotein) were heavily phosphorylated and N-glycosylated, of which 37 phosphorylation sites and 32 N-glycosylation sites were identified on vitellogenins-2. A Total of 30 N-glycosylation sites were identified on apolipoprotein-B (precursor of egg yolk low-density lipoprotein), but no phosphorylation site was identified. These phosphorylation and N-glycosylation of EYG proteins provide new insights for understanding the assembly structure and functional characteristics of EYG, thus contributing to its development and utilization.

Quantitative metabolome analysis of boiled chicken egg yolk

Boiling has important effects on the texture of chicken eggs, but its effects on egg nutrients have not been systematically investigated. In this study, changes in the metabolites of egg yolks boiled under different heating intensities were quantified and compared by metabolomic analysis. A total of 797 metabolites were identified, and the abundance of 162 metabolites changed significantly after boiling. The significant reduction of L-lysine and D-fructose suggested that Maillard reactions occurred in over-boiled egg yolks. Egg yolk endogenous enzymes might induce a partial hydrolysis of proteins and phospholipids during the warm-up period of boiling, as the abundance of dipeptides, lysophospholipids, and free fatty acids was significantly increased in boiled egg yolks. Boiling increased the detectable abundance of fat-soluble vitamins, riboflavin, and biotin, possibly by altering the complex structure of protein-lipid-lipophilic compounds or denaturing vitamin-binding proteins. The results of metabolomic analyses provide important information for understanding the nutritional changes of egg yolk boiled under different heating intensities.

Unveiling and application of the chicken egg proteome: An overview on a two-decade achievement

Egg proteins are not only the most complete and ideal form of protein for human or embryo nutrition but also play the vital role in the food industry. Egg proteins are subjected to many potential changes under various conditions, which may further alter the nutritional value, physicochemical-properties, and bioactivities of proteins. Recent advances in our understanding of the proteome of raw egg matrix from different species and dynamic changes occurring during storage and incubation are developing rapidly. This review provides a comprehensive overview of the main characteristics of chicken egg proteome, covering all its components and applications under various conditions, such as markers detection, egg quality evaluation, genetic and biological unknown identification, and embryonic nutritional supplementation, which not only contributes to our in-depth understanding of each constituent functionality of proteome, but also provides information to increase the value to egg industry.

Quantitative proteomic analysis provides insight into the survival mechanism of Salmonella typhimurium under high-intensity ultrasound treatment

The survival mechanism of Salmonella treated with high-intensity ultrasound (HIU) should be explored to further enhance the bactericidal efficacy of HIU. In this study, culturable Salmonella was reduced by applying HIU. Electron microscope imaging revealed that HIU caused the disintegration of cell structure and leakage of intracellular substances. For the Salmonella after the HIU treatment, key enzymes of the tricarboxylic acid [TCA] cycle were significantly downregulated, which led to a reduced ATP content (45.25%–75.00%), although ATPase activity was augmented by 33.82%–60.64% in the Salmonella. Accordingly, surviving Salmonella could have tolerated the stress of HIU by upregulating their environmental sensing (two-component system), chemotaxis (bacterial chemotaxis), substance uptake (ABC transporter), and ATP production (oxidative phosphorylation). Therefore, synergistically blocking the ATP production, signal transduction, or substance intake of Salmonella offer promising potential strategies to improve the bactericidal effect of HIU in industrial food processing.

•

Cell damage and substances leakage were observed in ultrasound treated Salmonella.

•

Ultrasonic treatments caused 1017 differentially expressed proteins in Salmonella.

•

Ultrasound inhibited tricarboxylic acid cycle and reduced adenosine triphosphate content in Salmonella.

•

Salmonella tolerated ultrasound by upregulating two-component system, ABC transport, and bacterial chemotaxis.

•

These altered pathways could be potential targets to enhance the lethality of ultrasound.

Egg yolk sialylglycopeptide: purification, isolation and characterization of N-glycans from minor glycopeptide species

Sialylglycopeptide (SGP) is a readily available naturally occurring glycopeptide obtained from hen egg yolk which is now commercially available. During SGP extraction, other minor glycopeptide species are identified, bearing N-glycan structures that might be of interest, such as asymmetrically branched and triantennary glycans. As the scale of SGP production increases, recovery of minor glycopeptides and their N-glycans can become more feasible. In this paper, we aim to provide structural characterization of the N-glycans derived from these minor glycopeptides.

Comparative Study on the Characterization of Myofibrillar Proteins from Tilapia, Golden Pompano and Skipjack Tuna

In this study, the physicochemical properties, functional properties and N-glycoproteome of tilapia myofibrillar protein (TMP), golden pompano myofibrillar protein (GPMP) and skipjack tuna myofibrillar protein (STMP) were assessed. The microstructures and protein compositions of the three MPs were similar. TMP and GPMP had higher solubility, sulfhydryl content and endogenous fluorescence intensity, lower surface hydrophobicity and β-sheet contents than STMP. The results showed that the protein structures of TMP and GPMP were more folded and stable. Due to its low solubility and high surface hydrophobicity, STMP had low emulsifying activity and high foaming activity. By N-glycoproteomics analysis, 23, 85 and 22 glycoproteins that contained 28, 129 and 35 N-glycosylation sites, were identified in TMP, GPMP and STMP, respectively. GPMP had more N-glycoproteins and N-glycosylation sites than STMP, which was possibly the reason for GPMP’s higher solubility and EAI. These results provide useful information for the effective utilization of various fish products.

Phosphoproteomic analysis of duck egg yolk provides novel insights into its characteristics and biofunctions

BACKGROUND

Although the importance of phosphorylation in the function of proteins is known, investigation of the protein phosphorylation of duck egg yolk (DEY) is still very limited. This study aimed to conduct a detailed phosphoproteomic study of DEY using immobilized metal affinity chromatography and ultra-high liquid chromatography tandem mass spectrometry.

RESULTS

A total of 253 phosphorylation sites assigned to 66 phosphoproteins were identified in DEY, of which VTG-1, VTG-2, and fibrinogen alpha chain were found to be the highly phosphorylated proteins in DEY. The biological functions of the identified phosphoproteins were illuminated through gene ontology analysis, which showed that they were mainly involved in binding, catalytic, immune response, and metabolic activity. S-X-E and S-X-S were found to be the most conserved serine motifs of phosphorylation in DEY. The comparison of DEY phosphoproteins with those of chicken egg yolk (CEY) revealed that differences mostly involved molecular functions and biological processes. The comparison also revealed a higher phosphorylation level in DEY proteins.

CONCLUSION

The higher phosphorylation level in DEY proteins than that in CEY proteins are supposed to help enhance duck growth performance and biological activities (e.g. antibacterial and antioxidant ability) for better adapting the humid environment the duck lived. © 2021 Society of Chemical Industry.

Integrated proteomic, phosphoproteomic, and N-glycoproteomic analyses of the longissimus thoracis of yaks

Yaks (Bos mutus) live in the Qinghai–Tibet plateau. The quality of yak meat is unique due to its genetic and physiological characteristics. Identification of the proteome of yak muscle could help to reveal its meat-quality properties. The common proteome, phosphoproteome, and N-glycoproteome of yak longissimus thoracis (YLT) were analyzed by liquid chromatography-tandem mass spectrometry-based shotgun analysis. A total of 1812 common proteins, 1303 phosphoproteins (3918 phosphorylation sites), and 204 N-glycoproteins (285 N-glycosylation sites) were identified in YLT. The common proteins in YLT were involved mainly in myofibril structure and energy metabolism; phosphoproteins were associated primarily with myofibril organization, regulation of energy metabolism, and signaling; N-glycoproteins were engaged mainly in extracellular-matrix organization, cellular immunity, and organismal homeostasis. We reported, for the first time, the “panorama” of the YLT proteome, specifically the N-glycoproteome of YLT. Our results provide essential information for understanding post mortem physiology (rigor mortis and aging) and the quality of yak meat.

•

A total of 2650 proteins were identified in yak longissimus thoracis.

•

Common proteins were involved mainly in myofibril structure and energy metabolism.

•

Phosphoproteins were associated with myofibrils, energy metabolism, and signaling.

•

N-glycoproteins were engaged mainly in ECM organization, immunity, and homeostasis.

Quantitative N-glycoproteome analysis of bovine milk and yogurt

Post-translational modification structure of food's proteins might be changed during processing, thereby affecting the nutritional characteristics of the food product. In this study, differences in protein N-glycosylation patterns between milk and yogurt were quantitatively compared based on glycopeptide enrichment, liquid chromatography separation, and tandem mass spectrometry analysis. A total of 181 N-glycosites were identified, among which 142 were quantified in milk and yogurt. Significant alterations in the abundance of 13 of these N-glycosites were evident after the fermentation of milk into yogurt. Overall, the N-glycosylation status of the majority of milk proteins remained relatively unchanged in yogurt, suggesting that their conformations, activities, and functions were maintained despite the fermentation process. Among the main milk proteins, N²⁴¹ of cathepsin D and N³⁵⁸ of lactoperoxidase were markedly reduced after undergoing lactic acid fermentation to produce yogurt. Furthermore, a comparative analysis of current and previously reported N-glycoproteomic data revealed heterogeneity in the N-glycosylation of milk proteins. To sum up, a quantitative comparison of the N-glycoproteomes of milk and yogurt was presented here for the first time, providing evidence that the fermentation process of yogurt could cause changes in the N-glycosylation of certain milk proteins.

•

181 N-glycosites from 118 N-glycoproteins were identified in milk and yogurt.

•

13 N-glycosites changed significantly after fermentation of milk into yogurt.

•

N²⁴¹ of cathepsin D and N³⁵⁸ of lactoperoxidase was markedly reduced in yogurt.

•

Heterogeneity of N-glycosylation of milk protein has been documented.

Quantitative proteomic analyses during formation of chicken egg yolk

A quantitative comparison of the proteomes during different periods of the formation of egg yolk, from yellow follicles (YF), small hierarchical follicles (9-12 mm, SF), and the largest hierarchical follicle (LF), was performed. The abundance of major egg yolk proteins (apolipoprotein B and vitellogenins) changed significantly during the yolk formation, and several protein hydrolases and isomerases, which may be related to the processing of egg yolk proteins, also varied significantly. The binding proteins for three vitamins (retinol, riboflavin, and vitamin D) and cholesterol were all most abundant in the LF period, suggesting that these nutrients were transported mainly at the final period of the egg yolk formation. Immunoglobulins decreased and complement proteins increased as formation progressed, indicating the dynamic nature of the egg yolk immune system. These results are helpful for understanding the nutrient composition, the formation of assembly structure, the preservation and processing properties of egg yolk.

Comparative N-glycoproteomic analysis of Tibetan and lowland chicken fertilized eggs: Implications on proteins biofunction and species evolution

The characterization and functionality of protein glycosylation among different related species are of common interest. Herein, non-standard quantification and N-glycosylation enrichment technology combined with ultra-high liquid chromatography-tandem mass spectrometry were used to establish detailed N-glycoproteomics of fertilized eggs, and quantitatively compared between Tibetan and lowland chicken. A total of 396N-glycosites from 143 glycoproteins were found. Specifically, compared with lowland chicken egg white, 32N-glycosites of 22 glycoproteins were up-regulated and 57N-glycosites of 25 glycoproteins were down-regulated in Tibetan chicken egg white. Also, 137N-glycosites in 72 glycoproteins showed much higher-degree glycosylation and 36N-glycosites in 15 glycoproteins displayed lower-degree glycosylation in Tibetan chicken egg yolk than those in lowland chicken egg yolk. Through bioinformatic analysis, these varied glycoproteins were highly associated with antifreeze activity, hypoxia adaptation, coagulation cascade, and binding/immunity activities, which may be related to plateau hypoxia and cold stress. PRACTICAL APPLICATIONS: These findings provide a new insight on the role of biological egg N-glycoproteins related to environmental adaptation and evolution, which may be further applied in improving egg processing and human health, by developing biomolecules for food and medical industry.

Bacteriostatic effects of high-intensity ultrasonic treatment on Bacillus subtilis vegetative cells

The bacteriostatic effects of high-intensity ultrasonic treatment (HIU) on Bacillus subtilis vegetative cells were evaluated, and the related mechanisms were explored using quantitative proteomics. The bacteriostatic effect of HIU on B. subtilis was proportional to the ultrasound treatment time and power, and the number of cultivable B. subtilis cells was decreased by approximately one log (at 270 W for 15 min) or half log (at 90 W for 25 min or 360 W for 5 min). Scanning electron microscopy images and gel electrophoresis results showed that HIU caused the destruction of the cell structure and intracellular protein leakage. In addition, HIU treatment at 270 W for 15 min resulted in the greatest decrease (84.22%) in intracellular adenosine triphosphate (ATP) content. The quantitative proteomic analysis showed that B. subtilis resisted the stress of HIU treatment by regulating the key proteins in physiological activities related to membrane transport (ATP-binding cassette [ABC] transporter), signal transduction (the two-component system), and energy metabolism (the tricarboxylic acid [TCA] cycle). HIU-induced physical damage, stress, and metabolic disorders were the main causes of the bacteriostatic effects on B. subtilis. These findings provide a foundation for the subsequent optimization and potential applications of HIU inactivation of B. subtilis.

Plasma membrane N-glycoproteome analysis of wheat seedling leaves under drought stress

Protein glycosylation is one of the ubiquitous post-translational modifications in eukaryotic cells, which play important roles in plant growth and adverse response. In this study, we performed the first comprehensive wheat plasma membrane N-glycoproteome analysis under drought stress via glycopeptide HILIC enrichment and LC-MS/MS identification. In total, 414 glycosylated sites corresponding to 407 glycopeptides and 312 unique glycoproteins were identified, of which 173 plasma membrane glycoproteins with 215 N-glycosylation sites were significantly regulated by drought stress. Functional enrichment analysis reveals that the significantly regulated N-glycosylation proteins were particularly related to protein kinase activity involved in the reception and transduction of extracellular signal and plant cell wall remolding. The motifs and sequence structures analysis showed that the significantly regulated N-glycosylation sites were concentrated within [NxT] motif, and 79.5% of them were located on the random coil that is always on the protein surface and flexible regions, which could facilitate protein glycosylated modification and enhance protein structural stability via reducing protein flexibility. PNGase F enzyme digestion and glycosylation site mutation further indicated that N-glycosylated modification could increase protein stability. Therefore, N-glycosylated modification is involved in plant adaptation to drought stress by improving the stability of cell wall remodeling related plasma membrane proteins.

Ovomucin may be the key protein involved in the early formation of egg-white thermal gel

Clarification of the mechanism of heat-induced gel formation by proteins under natural food systems could provide important references for the regulation of food texture. In the present study, the proteins involved in the early stage (heating at 72 °C for 8 min) of egg-white thermal gel (EWG) formation were studied quantitatively through comparative proteomic analysis. We discovered that the abundance of ovalbumin and ovomucoid increased significantly (p < 0.01), whereas that of ovotransferrin, lysozyme, ovomucin (mucin 5B and mucin 6) decreased significantly (p < 0.01), in the supernatant of EWG. If the initial interaction of egg white proteins was altered by ultrasonic pretreatment, the abundance of ovomucin and lysozyme in the supernatant of EWG increased, and was accompanied by the change from a solid gel to a fluid gel. Based on these results, we hypothesize that ovomucin has a key role in the formation and regulation of EWG properties.

Improvement of quality and flavor of salted egg yolks by ultrasonic assisted cooking

Physicochemical, texture indexes, microstructure and volatiles were used to characterize the changes in quality, structure and flavor of cooked salted egg yolks (SEYs) with or without ultrasonic treatment. Experimental results indicated that ultrasonic significantly increased cooking (water) loss, oil exudation, lipids oxidation (TBARS), accelerated the doneness of cooked SEYs and then promoted the generation of volatiles. These results were further confirmed by the improvement of thermal stability, the changes in color, secondary structure of proteins, water distribution and mobility. Meanwhile, more "fragments" and "cracks" were observed in scanning electron microscope (SEM) and the decrease in gumminess and chewiness were detected using texture profile analysis (TPA), inducing that the migration of lipids and collapse of gel network were intensified. Moreover, ultrasonic treatment decreased the content of sodium chloride in SEYs. Therefore, it was concluded that the doneness, quality and flavor of cooked SEYs were improved by ultrasonic treatment, which could be used as an effective and alternative method for the production of SEYs with good flavor, sandy and oily texture.

Egg white peptides ameliorate dextran sulfate sodium-induced acute colitis symptoms by inhibiting the production of pro-inflammatory cytokines and modulation of gut microbiota composition

Egg white peptides (EWPs) can be effectively used to alleviate and treat inflammatory diseases due to their anti-oxidation, anti-inflammation, and microbiota regulation capabilities. A dextran sodium sulfate (DSS)-induced colitis model was used to clarify the regulatory effects of EWPs on colitis. Forty-three peptide sequences were identified from EWPs using LC-MS/MS. The results demonstrated that EWPs decreased the levels of pro-inflammatory cytokines and the extent of crypt damage in a dose-dependent manner. 16S rRNA gene sequencing results indicated that 200 mg/kg EWPs significantly increased the relative abundance of beneficial bacteria Lactobacillus and Candidatus_Saccharimonas, and reduced the relative abundance of pathogenic bacteria Ruminiclostridium and Akkermansia. In addition, the degree of correlation between pro-inflammatory cytokines and microbiota was as follows: interleukin (IL)-1β > IL-8 > IL-6 > tumor necrosis factor-α To summarize, EWPs contributed to the alleviation of colitis symptoms and the intestinal injury through anti-inflammatory effects, repair of intestinal mucosa, and modulation of gut microbiota.

Tetrahydrocurcumin ameliorates Alzheimer's pathological phenotypes by inhibition of microglial cell cycle arrest and apoptosis via Ras/ERK signaling

1,7-bis(4-hydroxy-3-methoxyphenyl)heptane-3,5-dione (tetrahydrocurcumin, THC) is a major bioactive metabolite of curcumin, demonstrating the potential anti-inflammatory, antioxidant and neuroprotective properties, etc. In this study, it was found that Aβ induced decreased cell viability, cell cycle arrest and apoptosis in BV-2 cells, which were ameliorated by THC. In vivo, THC administration rescued learning and memory, and reduced Aβ burden in the hippocampus of APP/PS1 mice. By proteomic analysis of the hippocampus of mice, 157 differentially expressed proteins were identified in APP/PS1 mice treated with THC (comparing with APP/PS1 mice), which also suggested that the effects of THC on the cell cycle and apoptosis were mostly related to the "Ras signaling pathway", etc. In APP/PS1 mice, the down-regulation of Gab2 and K-Ras, and the up-regulation of caspase-3, TGF-β1 and TNF-ɑ were observed; THC attenuated the abnormal expression of Gab2, K-Ras, caspase-3 and TNF-ɑ, and up-regulated TGF-β1 and Bag1 expression. In BV-2 cells, Aβ induced the down-regulation of Gab2, K-Ras and TGF-β1, and the overexpression of caspase-3, PARP1, cleaved-PARP1 and TNF-ɑ, which were restored by THC. Moreover, THC up-regulated Bag1 expression in Aβ-treated BV-2 cells. The decreased transcriptional expression of Ccnd2 and Cdkn1a were also observed in Aβ-treated BV-2 cells, and THC alleviated the down-regulation of Ccnd2. For the first time, we identified that the action of THC in preventing AD was associated with inhibition of cell cycle arrest and apoptosis of microglia via the Ras/ERK signaling pathway, shedding new light on the role of THC in alleviating the progression of AD.

Depolymerization of chicken egg yolk granules induced by high-intensity ultrasound

The effects of high-intensity ultrasound (HIU) treatment-induced depolymerization of chicken egg yolk granules were investigated. The results showed that the yolk granules were depolymerized after HIU treatment, and the average particle size was significantly reduced from 289.4 nm (untreated) to 181.4 nm (270-W HIU treatment). All contents of dry matter, protein, calcium and phosphorus in the supernatant of the HIU-treated yolk granule solution increased, which suggests that HIU treatment increases the dissolution of yolk granule components. Spectroscopic analysis showed that HIU treatment increased the polarity of the microenvironment and enhanced the hydrogen bond force of yolk granules. These changes induced by HIU treatment collectively enhanced the zeta potential, decreased the free sulfhydryl group content, and slightly improved the emulsifying activity index of yolk granules. The present study reveals the depolymerization effect of HIU treatment on egg yolk granules and can inspire new potential applications of egg yolk granules.

Comparative N-Glycoproteomic Analysis Provides Novel Insights into the Deterioration Mechanisms in Chicken Egg Vitelline Membrane during High-Temperature Storage

The weakening of chicken egg vitelline membrane (CEVM) is one of the most important factors influencing egg quality during high-temperature storage. Therefore, a comparative N-glycoproteomic analysis of CEVM after 10 days of storage at 30 °C was performed to explore the roles of protein N-glycosylation in membrane deterioration. In total, 399 N-glycosites corresponding to 198 proteins were identified, of which 46 N-glycosites from 30 proteins were significantly altered. Gene ontology analysis revealed that these differentially N-glycosylated proteins (DGPs) were involved in antibacterial activity, glycosaminoglycan binding, lipid binding, and aminopeptidase activity. Removal of the N-glycans in Mucin-5B may result in a loss of CEVM's mechanical properties. The N-glycosites enriched in the apolipoprotein B β2 domain in CEVM were significantly changed, which may contribute to lipid composition modifications during storage. Moreover, N-glycosites in several metalloproteases were located within the functional domain or active site region, indicating that the decreased N-glycosylation levels may affect their structural stability, specific substrate binding, or enzyme activity. These findings provide novel insights into the roles of protein N-glycosylation during membrane weakening.

Phosphoinositide signaling plays a key role in the regulation of cell wall reconstruction during the postharvest morphological development of Dictyophora indusiata

The potential signaling mechanism of Dictyophora indusiata during postharvest morphological development was investigated through quantitative phosphoproteomic analyses. A total of 1566 phosphorylation sites changed significantly (872 upregulated and 694 downregulated) in the mature stage compared with those in the peach-shaped stage of D. indusiata. Bioinformatics analysis showed that the upregulated differentially phosphorylated proteins were mainly involved in the "phosphatidylinositol signaling system" and "mitogen-activated protein kinase signaling pathway-yeast", while the downregulated differentially phosphorylated proteins were related mainly to "starch and sucrose metabolism". Further mining of the phosphoproteome data revealed that upregulated phosphoinositide signaling activated the cell wall integrity pathway and then regulated the synthesis of the main components of the cell wall. The results suggested that phosphoinositide signaling could be a potential target pathway for the regulation of the postharvest morphological development of D. indusiata.

A puzzle piece of protein N-glycosylation in chicken egg: N-glycoproteome of chicken egg vitelline membrane

The chicken egg vitelline membrane (CEVM) is an important structure for the transmembrane transport of egg yolk components, protection of the blastodisc, and separation of egg white and egg yolk. In this study, the N-glycoproteome of the CEVM was mapped and analyzed in depth. Total protein of the CEVM was digested, and the glycopeptides were enriched by a hydrophilic interaction liquid chromatography microcolumn and identified by nano liquid chromatography/tandem mass spectrometry. A total of 435 N-glycosylation sites on 208 N-glycoproteins were identified in CEVM. Gene Ontology enrichment analysis showed that CEVM N-glycoproteins are mainly involved in the regulation of proteinases/inhibitors and transmembrane transport of lipids. Mucin-5B is the primary N-glycoprotein in the CEVM. Comparison of the main N-glycoproteins between the CEVM and other egg parts revealed the tissue specificity of N-glycosylation of egg proteins. The results provide insights into protein N-glycosylation in the chicken egg, CEVM functions and underlying mechanisms.

Integrated proteomic, phosphoproteomic and N-glycoproteomic analyses of chicken eggshell matrix

Eggshell matrix (EM) proteins play an important biological role in eggshell mineralization and embryo development. Many studies have demonstrated that some matrix proteins undergo posttranslational modifications, including phosphorylation and glycosylation, which have important regulatory effects on the functional properties of the proteins. Systematic analysis of the proteome, the phosphorylated modified proteome and the glycosylated modified proteome of the chicken EM was performed using a proteomics strategy. A total of 112 phosphorylation sites from 69 phosphoproteins and 297 N-glycosylation sites from 182 N-glycoproteins were identified in the chicken EM. Among all these identified modified proteins, 129 were not identified in the proteome (547 proteins). Therefore, a total of 676 EM proteins were identified in this study. Gene ontology (GO) enrichment analysis indicated that EM proteins and phosphoproteins were mainly enriched in regulation of enzyme activity, while EM N-glycoproteins were enriched in immune response regulation.

Quantitative N-glycoproteomic analyses provide insights into the effects of thermal processes on egg white functional properties

This study tries to elucidate the different mechanisms of functional properties among pasteurized egg white (P-EW), spray-dried egg white (SD-EW) and fresh egg white (F-EW) via quantitative N-glycoproteomic analyses. The results showed that spray-drying increased the surface hydrophobicity (181.4%) and zeta potential (25.6%) of egg white, which contributed to the enhancement of emulsifying activity index (20.1%) and foaming capacity (35.2%). Pasteurization caused the disintegration of natural protein aggregates in F-EW and resulted in a "block-like" P-EW gel and higher water holding capacity (6.2%). Spray-drying caused formation of thermal aggregates and led to a "mesh-like" SD-EW gel and better cohesiveness (3.6%). Quantitative N-glycoproteomic analysis showed that the abundance of 32 N-glycosites from 18 N-glycoproteins (such as Mucin 5B) of SD-EW was significantly reduced comparing to F-EW, indicated that the N-glycans of egg white protein are likely to be covalently cross-linked during spray-drying and are involved in thermal aggregation.

Omics analysis of holoproteins and modified proteins of quail egg

Confirmed to be a new type of food resource, quail egg can provide humans with high-quality protein and offer various nutrients that can promote growth and development. Post-translational modification of proteins can regulate their molecular structures and physiological functions. However, the understanding and related research of quail egg holoproteins and post-translationally modified proteins is not yet sufficient. This study provides an in-depth analysis of quail egg proteins using an omics strategy. A total of 175 proteins, 109 N-glycoproteins (293 N-glycosylation sites) and 23 phosphoproteins (84 phosphorylation sites) were identified. Motif analysis showed that N-glycosylation sites of quail eggs were classical sites. The main characteristic sequence of the phosphorylation site is "S-X-E" (77%). Functional analysis indicated that quail egg proteins, modified proteins were enriched in the regulation of enzyme activity. These results have significant reference value for understanding the structure, function of quail eggs, explaining the physicochemical reaction during the storage.

Quantitative Comparative Proteomic Analysis of Chicken Egg Vitelline Membrane Proteins during High-Temperature Storage

To explore the thermally induced alterations in chicken egg vitelline membrane (CEVM) protein abundances, a comparative proteomic analysis of CEVM after 10 days of storage at 30 °C was performed. Altogether, 981 proteins were identified, of which 124 protein abundances were decreased and 79 were increased. Bioinformatic analysis suggested that the altered proteins were related to structure (n = 10), mechanical properties (n = 13), chaperone (n = 15), antibacterial (n = 12), and antioxidant (n = 3). Alterations in abundances of structural proteins, possibly resulting from the disintegration of these complexes, were observed in this study, suggesting a loss in fibrous structure. Several proteins involved in mechanical strength (n = 10), elasticity (n = 3), and chaperone were decreased in abundances, which indicated that deficits in these proteins might affect the CEVM mechanical properties. These findings will extend our understanding of CEVM deterioration during high-temperature storage from a proteomic perspective.

A Comprehensive Identification of Chicken Egg White Phosphoproteomics Based on a Novel Digestion Approach

There are plenty of phosphoproteins in chicken egg white (CEW), which are of great significance for the biological activity and function of CEW. In this study, phosphorylated proteins in CEW were identified and analyzed based on two digestion strategies (trypsin and trypsin/glutamyl endoproteinase). Besides, the enrichment strategy of immobilized metal affinity chromatography was used, and phosphopeptides were identified by nano liquid chromatography/tandem mass spectrometry. A total of 189 phosphosites mapped onto 166 phosphopeptides corresponding to 96 phosphoproteins were identified. Gene ontology analysis suggested that these phosphoproteins of CEW mainly participated in biological processes such as "cell process", "biological regulation", and "response to stimulus". Moreover, the phosphoproteins of CEW were involved in molecular functions, primarily including "binding" and "catalytic activity". On the basis of the available literature, the research was the first comprehensive identification of chicken egg white phosphoproteins. This study further enriched the identification of phosphoproteins in CEW and laid a foundation for the subsequent study of phosphoproteins.

Quantitative proteomic and metabolomic analysis of Dictyophora indusiata fruiting bodies during post-harvest morphological development

The differences in Dictyophora indusiata fruiting bodies between peach-shaped and mature stage during the postharvest were systematically investigated through quantitative proteomic and metabolomic analyses. A total of 951 differentially expressed proteins were identified, 571 upregulated and 380 downregulated in the mature fruiting body; additionally, 173 upregulated and 165 downregulated differential abundance metabolites were screened. Integrated proteome and metabolome analyses showed that, during the maturation of D. indusiata fruiting bodies, glycerophospholipids were hydrolyzed and drastically decreased, the degradation of glucan was upregulated, the degradation and synthesis of chitin were simultaneously enhanced, and proteins were dominated via catabolism. Along with vigorous material metabolism, energy production was enhanced through the upregulated TCA-cycles and oxidative phosphorylation. In addition, the synthesis of antioxidant substances and the decomposition of peroxides were enhanced in mature fruiting bodies. These omics analyses of D. indusiata provide high-throughput data and reveal the changes in the post-harvest morphological development.

Phosphoproteomic analysis of duck egg white and insight into the biological functions of identified phosphoproteins

Phosphorylation of proteins is one of the most important and pleiotropic modifications. It plays a vital role in controlling protein functions. However, the phosphoproteome of duck egg white (DEW) has not been studied yet. To investigate the role of phosphorylation on DEW proteins, a detailed phosphoproteome analysis of DEW was performed using an immobilized metal affinity chromatography enrichment strategy. A total of 92 phosphosites representing 36 phosphoproteins were identified. [S-x-E] and [T-x-E] were found to be the most overrepresented motifs in DEW. The identified phosphoproteins in DEW were mainly involved in the binding, transport activity, biological regulation, and metabolic processes. Gene ontology analysis was used to elucidate the biological functions of DEW phosphoproteins and compare them with those of chicken egg white (CEW), which showed the differences mostly involved molecular functions and biological processes. PRACTICAL APPLICATIONS: These findings provide fundamental insight into the biological functions of identified phosphoproteins of DEW to better understand the roles of phosphorylated DEW proteins for food industries and human health. Phosphoproteomic study of DEW would be valuable for the food and nutrition industry to exploit the potential of this avian proteins in the processing of health benefit products.

Molecular aggregation and property changes of egg yolk low-density lipoprotein induced by ethanol and high-density ultrasound

Solvent and physical treatment are widely used in egg yolk processing, but the detailed changes in the molecular structure of egg yolk proteins during processing are unclear. The aim of this study was to investigate the effects of ethanol and ultrasonic treatments on chicken egg yolk low-density lipoprotein (LDL). The solubility, emulsifying activity and emulsifying stability decreased by 74.75%, 46.91%, and 81.58% after ethanol treatment, respectively. The average particle size of ethanol-treated LDL increased 13.3-fold to 937.85 nm. These results suggested that ethanol treatment induced wide-ranging aggregation of LDL. In contrast to ethanol treatment, ultrasonic treatment promoted the solubility and emulsifying stability of LDL and enhanced its zeta-potential (119.56%) and surface hydrophobicity (10.81%). Based on particle size analysis and transmission electron microscopy, approximately 34.65% of LDL had undergone aggregation and the molecular interface became more flexible after ultrasonic treatment. These results revealed the detailed changes in egg yolk LDL structure and properties during solvent (ethanol) and physical (ultrasound) processing.

Quantitative Comparative Integrated Proteomic and Phosphoproteomic Analysis of Chicken Egg Yolk Proteins under Diverse Storage Temperatures

To investigate the alterations of egg yolk protein abundances and their phosphorylation status at different storage temperatures, a comparative quantitative study of unfertilized chicken egg yolk after 15 days of storage at 4 and 37 °C was performed. Altogether, 445 proteins were identified in our study, of which the abundances of 154 proteins were significantly changed when comparing high-temperature storage with low-temperature storage, including 42 up-regulated and 112 down-regulated proteins. In the phosphoproteome, we identified a total of 137 phosphorylated sites on 326 peptides corresponding to 51 proteins. The results showed that the degree of phosphorylation for most egg yolk proteins was enhanced during high-temperature storage. Furthermore, GO analysis indicated that these phosphoproteins of egg yolk may be closely related to the binding, catalysis, and transport functions. The results provide further insights into the effect of storage temperature on egg proteome changes and their phosphorylation level. Moreover, this study can provide a theoretical basis for the improvement of egg quality during storage by phosphorylation modification in the food industry.

Comparative Quantitative Phosphoproteomic Analysis of the Chicken Egg during Incubation Based on Tandem Mass Tag Labeling

Protein phosphorylation plays an important role in protein structure and function. To investigate the role of egg protein phosphorylation in chicken embryonic development, a comparative and quantitative phosphoproteomic analysis of fertilized chicken egg white and yolk was performed during incubation. Overall, 215 phosphosites mapped onto 205 phosphopeptides corresponding to 100 phosphoproteins were identified. Among these phosphoproteins, 123 phosphosites from 62 egg proteins were found significantly changed (p < 0.05) at day 12 during incubation. Furthermore, GO analysis suggested that these differentially phosphorylated proteins were associated with various molecular functions, primarily including binding, molecular function regulator, and transport activity. Such findings in this study improved our understanding of the protein molecular functions involved in chicken embryonic development from a protein phosphorylation perspective.

De novo transcriptome and proteome analysis of Dictyophora indusiata fruiting bodies provides insights into the changes during morphological development

De novo transcriptome assembly and shotgun proteome analysis of Dictyophora indusiata fruiting bodies were performed. A total of 19,704 unigenes were sequenced, and 4380 proteins were identified. Annotation and functional analysis of the identified proteins were significantly enriched in small molecule synthetic and metabolic processes, protein modification regulation (phosphorylation and ubiquitination), and vesicle transport. Furthermore, quantitative developmental transcriptome analysis was performed between the peach-shaped and mature fruiting bodies, and the results revealed that the metabolism and transport activities were upregulated in the mature stage, while protein translation was downregulated; this regulation is likely the main reason for the significant changes in the nutrients of fruiting bodies. Furthermore, the cell wall stress-dependent MAPK sub-pathway was activated in the mature stage, and fungal cell wall degradation-related genes were upregulated, which could promote reconstruction of the cell wall and might play a key role in the morphological development of D. indusiata fruiting bodies.

Integrated Proteomic and N-Glycoproteomic Analyses of Chicken Egg during Embryonic Development

To better appreciate the alterations of egg proteins and their modifications during embryonic development, a comparative and quantitative study was performed aimed at chicken egg white and yolk proteome and N-glycoproteome after 12 days of incubation using tandem mass tag (TMT)-labeling technology in conjunction with reversed-phase high-performance liquid chromatography (RP-HPLC). A total of 334 unique N-glycosite-containing peptides from 153 N-glycoproteins were identified, of which 82 N-glycosite-containing peptides showed significant changes after 12 days of incubation. The varied proteome was mainly involved with antibacterial, ionic binding, cell proliferation, and embryonic development, while the different degrading and/or absorbing priorities of egg proteins were proposed. This study provides substantial insight into the effects of N-glycoprotein variations on the utilization of egg proteins by chicken embryo during incubation.

Comparative proteomic analysis of hen egg yolk plasma proteins during embryonic development

Avian egg yolk provides essential nutrients and physiological support for the developing embryo. To reveal the dynamics of yolk proteins during the entire period of incubation, we analyzed the alterations of egg yolk plasma proteins at different times during incubation (day 0, 7, 14, and 18). Day 14 (D14) of incubation was considered as the key point on the alteration of egg yolk proteins according to the SDS-PAGE analysis. The two-dimensional electrophoresis-based comparative proteomic analysis was conducted, and 26 spots representing 13 proteins were detected with significant changes in abundance. An accelerating transfer of ovalbumin from egg white into egg yolk was observed at D14 in fertilized eggs but not detected in unfertilized eggs, indicating an unrevealed absorbing pathway for the egg proteins/peptides particularly in fertilized eggs. Meanwhile, the abundance of yolk riboflavin-binding protein constantly decreased after D14, which might meet the need for essential riboflavin during embryo development. PRACTICAL APPLICATIONS: These findings provide fundamental insight into the effects of incubation on egg yolk plasma protein alterations during the entire embryonic development for a better understanding of plasma protein biological functions, especially in nutrient transportations and the formation of embryonic organs.